Abundance of iron and rock-forming elements in the galactic neighborhood, selected planets, and meteorites. The green data points are the iron-to-silicon (Fe/Si) molar ratio versus magnesium-to-silicon (Mg/Si) molar ratio of stars with planets in the Hypatia catalog by Hinkel et al. (2014), along with the 68% (1σ), 95% (2σ) and 99.7% (3σ) isocontours, and the (Fe/Si, Mg/Si) of the CI carbonaceous chondrites, Earth, Mercury, and some of the high-density exoplanets in Table 1. The Fe/Si and Mg/Si values of the high-density exoplanets and Mercury are unknown. Here we assume that these planets have a Mg/Si equal to that of CI chondrites (the high-density nature of these planets does not change if other Mg/Si values are assumed). We then derive the bulk Fe/Si of planets from estimates of their core-mass fraction, Z, based on the measured masses and radii. We convert Z into Fe/Mg versus Si/Mg using Equation (13) from Unterborn et al. (2023), assuming that all the iron of the planet is in the core and that the mantle is composed of SiO₂ and MgO. This plot is similar to Figure 7 from Unterborn et al. (2023), but here we plot only stars whose abundances [Fe/H], [Mg/H], and [Si/H] are known with uncertainties smaller than 30% and convert these values to molar ratios using the method by Hinkel et al. (2022).